The invention relates to a vehicle having a hybridized drive train and having a low-voltage onboard power supply system, which comprises electric consuming devices, an energy accumulator and a starter for an internal-combustion engine.
An electric onboard power supply is a complex electrical system. In German Patent Document DE 10 2007 017 187 A1, for example, an onboard power supply system with voltage-sensitive consuming devices of a vehicle is described which has an engine start-stop function. The voltage-sensitive consuming device is supported by way of a direct-voltage control element and a stop element.
German Patent Document DE 102 48 658 A1 describes the voltage-related support of power-sensitive consuming devices and high-power consuming devices by the parallel connection of a supercapicitor or a supercap module.
It is an object of the invention to provide an improved vehicle having a hybridized drive train and a low-voltage onboard power supply system, which comprises electric consuming devices, an energy accumulator and a starter for an internal-combustion engine.
This and other objects are achieved by a vehicle having a hybridized drive train and having a low-voltage onboard power supply system, which comprises electric consuming devices, an energy accumulator and a starter for an internal-combustion engine. The low-voltage onboard power supply system further comprises a support accumulator. The low-voltage onboard power supply system has a first switch between the support accumulator and the additional low-voltage onboard power supply system.
According to the invention, the low-voltage onboard power supply system comprises a support accumulator and a first switch between the support accumulator and the additional low-voltage onboard power supply system.
The vehicle further has a bidirectional direct-voltage control element, which comprises a first interface and a second interface, the first interface being connected with the support accumulator and the second interface being connected with the low-voltage onboard power supply system.
A second switch of the low-voltage onboard power supply system has the effect that the second interface of the direct-voltage control element and the energy accumulator can be electrically separated from the additional low-voltage onboard power supply system.
The starter of the internal-combustion engine of the hybridized drive train is situated between the energy accumulator and the second interface of the direct-voltage control element.
By way of the starter, the internal-combustion engine can be additionally started (additional start) during the driving operation of the vehicle, so that traction energy can also be provided from power of the internal-combustion engine.
During the driving operation of the vehicle, the first switch and the second switch are closed; before an additional start, the second switch is opened; after the additional start, the second switch is closed; during an afterunning of the vehicle, the support accumulator is partially discharged, and subsequently, the first switch is opened; during a stationary operation of the vehicle, the first switch is opened, and during a prerunning of the vehicle, the support accumulator is charged by way of the direct-current control element, and subsequently, the first switch is closed.
This means that, at an additional start of the internal-combustion engine in the driving operation, the consuming devices are uncoupled from the electric potential of the energy accumulator and are supported by the support accumulator.
When, in an afterrunning phase, the vehicle is changed from the driving operation to a rest condition—also called “falling asleep of the vehicle”—the support accumulator is discharged and the first switch is opened. Therefore, no direct electric connection exists between the support accumulator during the phase of the vehicle without any driving operation and the remaining low-voltage onboard power supply system. This is advantageous, for example, in the case of power-optimized support accumulators.
When, in a prerunning phase, the vehicle is changed from the rest condition to the driving operation—also called “awaking of the vehicle”—, the support accumulator is precharged by way of the direct-voltage control element and the first switch is closed.
At the beginning of the driving operation, the support accumulator is therefore at the potential of the low-voltage onboard power supply system and supports the consuming devices, particularly during an additional start when the second switch is open.
As an alternative, the vehicle may also have an expanded onboard power supply system with high-power consuming devices and with an additional accumulator and a bidirectional direct-voltage control element, which comprises a first interface and a second interface, the first interface being connected with the support accumulator and the second interface being connected with the expanded onboard power supply system.
It will then be particularly advantageous for the low-voltage onboard power supply system to have a second switch, and, by means of the second switch, the energy accumulator can be electrically separated from the additional low-voltage power supply system. The starter is connected in parallel with respect to the energy accumulator.
During the driving operation of the vehicle, the first switch and the second switch are closed; before an additional start, the second switch is opened; after the additional start, the second switch is closed; during an afterunning of the vehicle, the support accumulator and the additional accumulator are partially discharged, and subsequently, the first switch is opened; during a stationary operation of the vehicle, the first switch is opened; during a prerunning of the vehicle, the support accumulator is charged by way of the direct-current control element, and subsequently, the first switch is closed and, during the prerunning, the additional accumulator is charged by way of the direct voltage control element.
This means that, at an additional start of the internal-combustion engine in the driving operation, the consuming devices are uncoupled from the electric potential of the energy accumulator and are supported by the support accumulator. The high-power consuming devices are supported by the additional accumulator.
When, in an afterrunning phase, the vehicle is changed from the driving operation to a rest condition—also called “falling asleep of the vehicle”—the support accumulator and the additional accumulator are discharged and the first switch is then opened. Therefore, no direct electric connection exists between the support accumulator during the phase of the vehicle without any driving operation and the remaining low-voltage onboard power supply. This is advantageous, for example, in the case of power-optimized support accumulators.
When, in a prerunning phase, the vehicle is changed from the rest condition to the driving operation—also called “awaking of the vehicle”—, the support accumulator is precharged by way of the direct-voltage control element and the first switch is closed. Subsequently, a precharging of the additional accumulator takes place by way of the direct-voltage control element.
At the beginning of the driving operation, the support accumulator is therefore at the potential of the low-voltage onboard power supply system and supports the consuming devices particularly during an additional start when the second switch is open. At the start of the driving operation, the additional accumulator is at a predeterminable potential in order to support the high-power consuming devices in a voltage-related manner.
The invention is based on the considerations indicated in the following.
There are vehicles which have a classical 12 V onboard power supply system for supplying electric energy. The classical 12 V architecture is incapable of meeting future demands by high-power consuming devices, such as, for example, chassis systems (electric roll stabilization, electric active steering system) or additional engine starting systems in the case of hybrid vehicles or vehicles having an engine start-stop function.
There is therefor provided an expansion of the conventional vehicle onboard power supply system with respect to its architecture by one voltage level to 48 V for high-power consuming devices and to equip the 12 V onboard power supply system with a dynamic support accumulator and two switches.
An operating strategy is provided for the two switches, which strategy permits a charging of the dynamic support accumulator with the termination of the rest condition of the vehicle. This charging is called precharging.
This contributes to the stabilization of the energy supply in the vehicle, for example, in the case of additional starts and in the case of driving maneuvers.
The total weight of the energy accumulators that are used can be minimized when, for example, a supercapacitor is used as the dynamic additional accumulator and a lead battery can be dimensioned to be smaller.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.